Theoretical Studies on the Photoelectron and Absorption Spectra of MnO 4 – and TcO 4 –
The tetraoxo pertechnetate anion (TcO4-) is of great interest for nuclear waste management and radiopharmceuticals. To elucidate its electronic structure and to compare with that of its lighter congener MnO4-, the photoelectron and electronic absorption spectra of MnO4 - and TcO4 - are investigated with density functional theory (DFT) and ab initio wave function theory (WFT). The vertical electron detachment energies (VDEs) of MnO4 - obtained with the CR-EOM-CCSD(T) method are in good agreement with the lowest two experimental VDEs; the differences are less than 0.1 eV, representing a significant improvement over the IP-EOMCCSD(T) result in the literature. Combining our CCSD(T) and CR-EOMCCSD( T) results, the first five VDEs of TcO4 - are estimated between 5 and 10 eV with an estimated accuracy of about ±0.2 eV. The vertical excitation energies are determined by using TD-DFT, CR-EOM-CCSD(T), and RASPT2 methods. The excitation energies and the assignments of the spectra are analyzed and partly improved. They are compared with reported SAC-CI results and available experimental data. Both dynamic and nondynamic electron correlations are important in the ground and excited states of MnO4 - and TcO4 -. Nondynamical correlations are particularly relevant in TcO4 - for reliable prediction of excitation energies. In TcO4 - one Rydberg state interlaces but does not mix with the valence excited states, and it disappears in the condensed phase.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1097929
- Journal Information:
- Inorganic Chemistry, Vol. 52, Issue 17; ISSN 0020-1669
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
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